This study will address ecologically-based questions concerning predictors of socioemotional development and physical growth among daycare and homecare infants. Specifically, we propose to study a number of key issues which are central to the current controversy in the field of infant daycare. First, we will examine the effects of age of entry to daycare on the socioemotional development of infants. This aim will be referred to as the Entry proposition. Second, we will differentiate between effects associated with initial stay and subsequent stay in daycare. We refer to this aim as the Transitional stay proposition. Last, a-priori, personal, family and environmental variables characterizing children who are sent to daycare will be examined compared with children who stay at home. We refer to this aim as the Background proposition. Also, we intend to observe the physical growth and thrive of the target population, and to examine whether the growth and thrive during the first year of life differ for daycare and home reared infants. Along the same line of the possible effects of a-priori identified, infant characteristics, it is equally possible that the first year of life is characterized with a differential quality of thrive which eventually could play a role in deciding about what type of care arrangement to select for the child. Or vice versa, physical growth may prove to be an important outcome measure. As much as we are interested in understanding each of these aims on its own, our research aims and design will also acknowledge the possibility of interactions among the stated propositions. Or to state our interactional-ecological interest differently: Under what circumstances are what outcomes associated with what conditions of daycare, to what extent and why? These research aims will be studied in a prospective-longitudinal research design. Some of the variables pertaining to the above specified aims will be observed directly, some will be observed statistically. Among the variables directly investigated are age of entry, transitional stay, ethnic origin, and SES. Thus the basic design will be as follows: Age of entry (6-8; 9-11; 12-14 months) including an additional group of home reared infants x Ethnic Origin (Sephardic; Ashkenazy; Indeterminant) x SES (lower, middle) as between variables x transition (0-3 months; 4 months and above) as a within variable, all together comprising twenty- four groups, each consisting of 30 subjects (N-720). The measures to be assessed across these groups are: Infant Behavior Questionnaire, Infant Temperament Assessment, Ainsworth Strange Situation, Attachment Q-Set, Physical examination, Attachment Indicators During Stress, Maternal Separation Anxiety Scale, The Depression Adjective Check List, role Satisfaction Scale, The Nursing Child Assessment Feeding and Teaching Scales, Dyadic Adjustment Scale, SES and demographic information, Social Contacts and Social Supports Scales, HOME Scale, Life Events Questionnaire, Infant-Toddler Center Spot Observation System, Structure of Day Care, and Caregiver Characteristics.